1. Field of the Invention
The present invention relates to a single chip including a plurality of elements and a method of fabricating the same, and more particularly, to a subminiature single chip fabricated on a single substrate by fabricating a predetermined cavity in one of a plurality of elements and then positioning another element in the cavity, and a method of fabricating the same.
2. Description of the Related Art
Recent developments in electronic technology have resulted in electronic devices that have various and excellent functions and that are compact and light. In particular, such electronic devices have been made compact and light more rapidly due to advances in Micro Electro Mechanical System (MEMS) technology. In MEMS technology electrical and mechanical components are made on a single micro body. In other words, MEMS technology combines micro scale mechanical and electrical structures to fabricate a system having a new function.
A plurality of structures and a plurality of circuit units fabricated using such MEMS technology can be interconnected to develop various types of single chips.
FIGS. 1A and 1B are views illustrating the structure of a gyro-sensor as an example of such a single chip in which a plurality of structures and a plurality of circuit units are disposed on a plane. In other words, FIG. 1A is a plan view of a gyro-sensor, and FIG. 1B is a cross-sectional view of the gyro-sensor shown in FIG. 1A.
The gyro-sensor is an apparatus which detects a circular angular velocity using a principle of generating a Coriolis force in a third axis direction orthogonal to first and second axis directions by receiving a rotation force of a constant angular velocity in the second axis direction perpendicular to a mass uniformly vibrating in the first axis direction. In other words, when the mass rotates toward the third axis direction due to the Coriolis force, the gyro-sensor changes the displacement of the mass into a variation in capacitance to detect the circular angular velocity. Thus, the gyro-sensor requires a mass vibrating in a predetermined direction and a sensing electrode to generate and sense the Coriolis force. The mass and the sensing electrode can be fabricated using MEMS technology.
Referring to FIG. 1A, in the gyro sensor, a MEMS structure 11, an analog Application Specific Integrated Circuit (ASIC) 12, and a digital ASIC 13 are disposed on a substrate 10 in a predetermined pattern. The MEMS structure 11 includes a mass, a sensing electrode, and the like. The analog ASIC 12 detects a variation in capacitance from the MEMS structure 11 and converts the variation into an analog voltage signal proportional to a circular angular velocity. Thus, the digital ASIC 13 converts the analog voltage signal output from the analog ASIC 12 into a digital signal and outputs the digital signal to the outside.
FIG. 1B is a cross-sectional view of the gyro-sensor shown in FIG. 1A. Referring to FIG. 1B, the MEMS structure 11 is electrically coupled to the analog ASIC 12 via conductive materials 14.
In the gyro-sensor shown in FIGS. 1A and 1B, various structures and circuit units are disposed on a plane. Thus, the whole area of the single chip increases. Therefore, the gyro-sensor is not suitable for the recent tendency toward miniaturization.
FIGS. 2A and 2B illustrate the structure of a conventional gyro-sensor including a stack of a MEMS structure 21, an analog ASIC 22, and a digital ASIC 23. Referring to FIG. 2A, the MEMS structure 21 is formed on a substrate 20, and various circuit units such as the analog and digital ASICs 22 and 23 are formed on the MEMS structure 21. Next, the MEMS structure 21, the analog ASIC 22, and the digital ASIC 23 are electrically coupled to one another via wires 24. FIG. 2B is a cross-sectional view of the gyro-sensor shown in FIG. 2A.
As shown in FIGS. 2A and 2B, the whole area of the gyro-sensor may be more reduced than that of the gyro-sensor in which elements are disposed on a plane. However, a plurality of elements are stacked, and then wire bonding is performed. Thus, the volume of the gyro-sensor is increased. Thus, the gyro-sensor is not suitable to be used in recent compact, light electric devices. Also, when the wire bonding is performed, loss of wires may occur.